Magnetic Raman scattering of the ordered tetrahedral spin-1/2 clusters in Cu_2Te_2O_5(Br_(1-x)Cl_x)_2 compounds

TL;DR

This study investigates magnetic Raman scattering in Cu_2Te_2O_5(Br_(1-x)Cl_x)_2 compounds, revealing how doping alters magnetic excitations and order, with hybridization effects and spin reorientation observed.

Contribution

It introduces a dimerized spin model for tetrahedral Cu-clusters and explains the effects of Cl doping on magnetic excitations and order parameter changes.

Findings

Longitudinal magnetic excitation hybridizes with singlet excitation in pure Br system.

Magnetic scattering intensities change significantly with Cl doping.

Spins reorient perpendicular to each other for x > 0.25.

Abstract

Raman light-scattering experiments in the antiferromagnetic phase of the Cu_2Te_2O_5(Br_(1-x)Cl_x)_2 compounds are analyzed in terms of a dimerized spin model for the tetrahedral Cu-clusters. It is shown that the longitudinal magnetic excitation in the pure Br system hybridizes with a localized singlet excitation due to the presence of a Dzyaloshinskii-Moriya anisotropy term. The drastic change of the magnetic scattering intensities observed when a proportion of Br is replaced by Cl ions, is proposed to be caused by a change of the magnetic order parameter. Instead of being parallel/antiparallel with each other, the spins in the two pairs of spin-1/2 order perpendicular to each other, when the composition x is larger than about 0.25.